Tires on industrial equipment are constantly exposed to sharp objects, including metal, glass, thorns, and rocks, making them the most vulnerable part of such equipment. Consequently, flat tires are a common cause for equipment down time.
In response to these problems, a number of methods have been developed to flatproof tires. One such method replaces the air in a tire with polyurethane, neoprene, or other suitable polymeric materials. The polymeric materials may either be dry filled into the tire as solid particles, or may be liquid filled into the tire as a mixture of reactants which cures over time into a solid polymeric mass.
In the liquid fill method, the valve stem core is removed from the valve stem of the tire, and the tire is deflated to atmospheric pressure. A device for pressure filling the tire is then attached to the valve stem for filling the tire with liquid reactants. As the tire fills with the liquid, air in the tire rises to the top of the tire and is allowed to escape through a suitable perforation in the tire casing. When the tire is completely filled with liquid, as indicated by the emission of liquid from the perforation, the flow of liquid into the tire is stopped and the perforation blocked. Then, additional liquid is added until a desired pressure is achieved.
Because the valve stem core has been removed from the valve stem to allow introduction of the liquid reactants, it is necessary upon completion of filling to block the valve stem while the polymeric mixture in the tire is curing. Presently, this is accomplished by replacing the valve stem core after the tire has been filled. The tool commonly used for this purpose has a barrel that fits over the valve stem at one end. The other end of the barrel is connected to hoses that supply the liquid reactants to the tire. A syringe-like device extends through the center of the barrel and has a plunger upon which the replacement valve stem core is mounted. In use, the plunger is carefully manipulated inward until the replacement valve stem core is aligned with the threaded surface on the interior of the valve stem. The plunger is then twisted to screw the valve stem core into place in the valve stem.
This prior method, thus requires one to follow for each tire the steps of (1) removing the valve stem core, (2) attaching the barrel, (3) filling the tire, (4) replacing the valve stem core while the liquid polymer pressure is maintained, and (5) detaching the barrel. After this is accomplished for one tire, the worker moves to the next tire and repeats the same steps. With regard to step (4), it should be remembered that the valve stem is very small, and properly aligning the replacement valve stem core with the threaded surface in the valve stem is cumbersome and time consuming in practice, thus contributing to the high cost of flatproofing.